Control system for drawworks operations

A method for monitoring and controlling a drawworks including a rotatable drum on which a line is wound, wherein the drawworks and the line are used for facilitating movement of a load suspended on the line, the method comprising:

• connecting a brake arrangement to the rotatable drum for limiting the rotation of the rotatable drum;
• connecting at least one electrical motor to the rotatable drum for driving the rotatable drum;
• producing a load signal representative of the load suspended on the line;
• producing a calculated torque value based on the load signal and electrical motor capacity;
• and
• generating pre-torquing of the electrical motor;
• and
• commencing a gradual release of the brake arrangement from the rotatable drum;
• wherein, unless the rotation of the rotatable drum is in a lowering direction, transferring control of the rotation of the rotatable drum to the electrical motor while fully releasing the brake arrangement from the rotatable drum when the electrical motor pre-torquing level is substantially equal to the calculated torque value;
• and
• wherein, when the rotation of the rotatable drum is in a lowering direction, engaging the brake arrangement to limit rotation of the rotatable drum and increasing the calculated torque value;
• wherein, when the rotation of the rotatable drum is no longer in a lowering direction, transferring control of the rotation of the rotatable drum to the electrical motor while fully releasing the brake arrangement from the rotatable drum when the electrical motor pre-torquing level is substantially equal to the increased calculated torque value.

A system for monitoring and controlling a drawworks including a rotatable drum on which a line is wound, wherein the drawworks and the line are used for facilitating movement of a load suspended on the line, the system comprising:

• a brake arrangement connected to the rotatable drum for limiting the rotation of the rotatable drum;
• at least one electrical motor connected to the rotatable drum for driving the rotatable drum;
• a load signal representative of the load on the line;
• a calculated torque value based on the load signal and electrical motor capacity;
• a drawworks control system for providing a signal representative of the calculated torque value to the electrical motor wherein pre-torquing is generated in the electrical motor in response to said signal;
• and
• wherein control of the rotatable drum is transferred from the brake arrangement to the electrical motor.

A drilling rig comprising:

• a derrick;
• a traveling block, suspended from the derrick by a line connected to an anchor, for facilitating upward and downward movement of associated equipment into and out of a well bore;
• a drawworks including a rotatable drum on which the line is wound;
• at least one electrical motor connected to the rotatable drum for driving the rotatable drum;
• a brake arrangement for limiting rotation of the rotatable drum;
• a measuring device for producing a load signal representative of the load on the traveling block;
• and
• a drawworks control system for providing a calculated torque value based on the load signal and electrical motor capacity and for providing a signal representative of the calculated torque value to the electrical motor wherein pre-torquing is generated in the electrical motor in response to said signal;
• wherein control of the rotatable drum is transferred from the brake arrangement to the electrical motor;
• the drawworks control system provides a disabling signal to the brake arrangement and a control signal to the electrical motor to transfer control of the rotatable drum when the electrical motor pre-torquing level is substantially equal to the calculated torque value.